Development and Application of a High-Performance Liquid Chromatography Stability-Indicating Assay for Beyond-Use Date Determination of Compounded Topical Gels Containing Multiple Active Drugs.

Topical gels compounded by pharmacists are important clinical tools for the management of pain. Nevertheless, there is often a dearth of information about the chemical stability of drugs included in these topical formulations, complicating the assignment of beyond-use dating. The purpose of this study was to develop a high-performance liquid chromatography photodiode array-based stability-indicating assay that could simultaneously resolve six drugs (amitriptyline, baclofen, clonidine, gabapentin, ketoprofen, lidocaine) commonly included in topical gels for pain management and their potential degradation products. Furthermore, this method was applied to the determination of beyond-use dating of combinations of these drugs prepared in commonly utilized bases (Lipobase, Lipoderm, Pluronic organogel). Gabapentin was determined to be the least stable component in all formulations tested. Measured stability ranged between 7 to 49 days depending on the base and other active drugs present in the formulation. In the absence of gabapentin, baclofen was the next least stable component, lasting for 120 days, regardless of the type of formulating base used.

Stability of an Extemporaneously Compounded Oral Suspension of Bosentan.

PURPOSE: To assess the stability of an extemporaneously compounded oral suspension of bosentan from commercially available tablets for a period of 1 month. METHODS: A 6.25 mg/mL oral suspension of bosentan monohydrate was prepared from Tracleer tablets. The bosentan suspension was then evenly divided between 2 light-resistant prescription bottles and stored in the dark either under refrigeration (4-8°C) or at controlled room temperature (21-26°C). The suspensions were assessed for physical changes (ease of resuspendability, change in color, change in odor), and samples were drawn immediately after preparation and on days 0, 1, 3, 7, 10, 14, 21, 28, and 31. Samples were analyzed at each time point by high-performance liquid chromatography (HPLC) utilizing a reversed-phase column with chemical stability defined as the retention of at least 90% of the initial intact bosentan concentration measured. RESULTS: No change in suspendability, color, or odor of the compounded bosentan suspensions was noted throughout the storage period. Furthermore, regardless of storage conditions, the oral suspension of bosentan retained at least 94% of the active pharmaceutical ingredient for 31 days after preparation. CONCLUSION: The results of our study indicate that a 6.25 mg/mL bosentan oral suspension stored in the dark under refrigeration and at room temperature maintains physical and chemical stability for 1 month.

Chiral stability of an extemporaneously prepared clopidogrel bisulfate oral suspension.

OBJECTIVES: The purpose of this study was to evaluate the chiral stability of clopidogrel bisulfate in an extemporaneously compounded oral suspension for a period of 60 days. METHODS: A 5 mg/mL oral suspension of clopidogrel bisulfate was prepared from commercially available Plavix tablets. The clopidogrel suspension was then evenly divided between two light-resistant prescription bottles and stored either under refrigeration (4°C) or at room temperature (25°C). Samples were drawn from the stored suspensions immediately after preparation and on days 7, 14, 28, and 60. Samples were subsequently analyzed at each time point by high-performance liquid chromatography using a reversed-phase column, with chemical stability defined as the retention of at least 90% of the initial intact clopidogrel concentration measured. To determine the chiral stability of the suspension, samples were also analyzed by high-performance liquid chromatography using a chiral column to investigate possible enantiomeric inversion. Chiral stability was defined as the retention of at least 90% of the initial concentration of the suspension as the S-enantiomer, the active moiety of Plavix. RESULTS: Regardless of storage conditions, the oral suspension of clopidogrel retained at least 98% of the active S-enantiomer for 60 days after preparation. Compared with the clopidogrel suspension stored in the refrigerator, more chiral inversion was noted in the clopidogrel suspension stored at room temperature. CONCLUSIONS: Our investigation of chiral stability indicates that a 5 mg/mL clopidogrel oral suspension stored under refrigeration and at room temperature maintains chiral stability as the active S-enantiomer.

Rho-kinase inhibitors offer a new approach in the treatment of glaucoma.

INTRODUCTION: Primary open-angle glaucoma (POAG) is a leading cause for worldwide blindness and is characterized by progressive optic nerve damage. The etiology of POAG is unknown, but elevated intraocular pressure (IOP) and advanced age have been identified as risk factors. IOP reduction is the only known treatment for glaucoma. Recently, drugs that inhibit rho-associated protein kinase (ROCK) have been studied in animals and people for their ability to lower IOP and potentially treat POAG. ROCK inhibitors lower IOP through a trabecular mechanism and may represent a new therapeutic paradigm for the treatment of POAG. AREAS COVERED: Exploring the place that ROCK inhibitors may occupy in our treatment of POAG requires a thorough understanding of pathophysiology and treatment. This article summarizes current research on the incidence, proposed etiologies and mechanisms of action for this drug class. ROCK inhibitor research is presented and considered in light of the current standard of pharmacologic care. EXPERT OPINION: ROCK inhibitors alter the cell shape and extracellular matrix (ECM) of the trabecular meshwork. Preclinical studies demonstrate that these drugs have the potential to become a new therapy for glaucoma. However, ROCK inhibitors can affect multiple cell types, and their utility can be proven only after clinical studies in patients.

Effect of formulation pH on transdermal penetration of antiemetics formulated in poloxamer lecithin organogel.

The purpose of this study was to assess the impact of altering formulation pH on the transdermal penetration of several commonly used antiemetic, weakly basic drugs incorporated into poloxamer lecithin organogel vehicle. Poloxamer lecithin organogel formulations containing promethazine hydrochloride (25 mg/mL), metoclopramide hydrochloride (10 mg/mL), and ondansetron hydrochloride (8 mg/mL) were examined for both drug release and transdermal penetration across porcine skin in modified Franz diffusion cells for a period of 24 hours. For the transdermal studies, each antiemetic drug was formulated at a pH above and below their acid dissociation constant (pKa) in an attempt to assure that the drug would be primarily in their respective ionized or non-ionized states. In addition, drug content in skin was assessed at the end of the 24-hour experiment. Drug content analysis was determined via high-performance liquid chromatography. As a percent of total drug release from the poloxamer lecithin organogel vehicle, promethazine hydrochloride demonstrated the most transdermal drug penetration after 24 hours (30.2% +/- 20.2%), followed by ondansetron hydrochloride (2.7% +/- 1.1%) and metoclopramide hydrochloride (1.8% +/- 1.6%). Subsequently, the pH of the Pluronic F-127 gel was adjusted in order to ensure that each antiemetic drug would be primarily in its unionized state. The transdermal permeation of each antiemetic drug primarily in its unionized state increased over that observed with the drug primarily in its ionized state after 24 hours (promethazine: 1.6-fold increase; metoclopramide: 1.3-fold increase; ondansetron: 1.8-fold increase). A similar trend was noted in the amount of each drug found in the skin after 24 hours (promethazine: 1.2-fold increase; metoclopramide: 2.4-fold increase; ondansetron: 3.0-fold increase). These results suggest that proper optimization of drug ionization state may be a useful strategy for compounding pharmacists to increase the efficacy of drugs intended for inclusion in transdermal formulations.

The effect of Rho-associated kinase inhibition on the ocular penetration of timolol maleate.

PURPOSE: To assess the effects of Rho-associated kinase (ROCK) inhibition on the intraocular penetration of timolol maleate. METHODS: Ex vivo porcine corneal penetration of timolol maleate, sotalol hydrochloride, or brinzolamide incubated with or without Y-27632 was determined in vertical Franz diffusion cells. The effect of ROCK inhibition on the vasodilation of porcine conjunctival vasculature was assessed by scanning electron microscopy (SEM) and immunohistochemical staining with subsequent laser-scanning confocal microscopy (LSCM). Experiments were conducted in New Zealand White (NZW) rabbits to assess the effect of ROCK inhibition on the intraocular distribution of timolol maleate. RESULTS: ROCK inhibition resulted in minimal alteration of ex vivo porcine corneal drug penetration of timolol, sotalol, or brinzolamide. SEM and LSCM experiments conducted with conjunctiva and sclera tissue in Franz diffusion cells suggested vasodilation in the conjunctival vasculature in the presence of Y-27632. Pretreatment of the eyes of NZW rabbits with Y-27632 resulted in aggregate fold reductions (1 hour, 0.25-fold; 4 hours, 0.45-fold) of timolol maleate drug concentrations in intraocular tissues (aqueous humor, lens, and iris) versus eyes not receiving Y-27632 pretreatment. Pretreatment with a vasoconstrictor, phenylephrine, resulted in a reversal of the effect of Y-27632 on diminished timolol maleate intraocular penetration in NZW rabbits. CONCLUSIONS: ROCK inhibition reduced the intraocular penetration of administered timolol maleate presumably due to increased systemic elimination through the conjunctival vasculature. It is anticipated that care in order and timing of ROCK inhibitor administration will be warranted for those patients who may be on a multiple topical drug regimen for primary open-angle glaucoma.

Reestablishment of the nasal permeability barrier to several peptides following exposure to the absorption enhancer tetradecyl-beta-D-maltoside.

Regular insulin, NPH insulin, glargine insulin, calcitonin, and human growth hormone were administered to rats nasally with 0.125% tetradecyl-beta-D-maltoside (TDM), or at various times after TDM treatment. Absorption of all five peptides was enhanced initially and diminished in a time-dependent manner as the interval between administration of TDM and the peptide increased. Changes in nasal morphology were also assessed via transmission electron microscopy (TEM) immediately after TDM treatment and at various times thereafter. TEM analysis demonstrated that 0.125% TDM caused a rapid and transient alteration in the morphology of the apical membrane surface. Fewer cilia were observed and cell-cell junctions were difficult to visualize, but no epithelial cell erosion was apparent. Two hours after TDM treatment, the apical membrane surface once again contained abundant cilia and cell-cell junctions were readily visualized. The complete recovery of the nasal permeability barrier to several different peptides following TDM administration and the concomitant histological evidence demonstrate that TDM treatment transiently perturbs the nasal mucosa to stimulate peptide drug absorption and does not produce irreversible damage to the cells that line the nasal cavity.

Eyedrops containing SA9000 prodrugs result in sustained reductions in intraocular pressure in rabbits.

AIM: Poor topical bioavailability and ocular irritation have impeded the development of the diuretic, ethacrynic acid (ECA) as a clinically useful ocular hypotensive for the treatment of glaucoma. Thus, the development of analogs and prodrugs of analogs with improved ocular penetration, potency, and tolerability is required. The aim of this work is to evaluate the corneal penetration and ocular distribution of SA9000, an ECA analog. Novel SA9000 prodrugs intended to further improve ocular pharmacodynamic effect were also evaluated. RESULTS: SA9000 penetrated porcine corneas more effectively than ECA in corneal diffusion studies. In vivo studies in Dutch-belted (DB) rabbits indicated that topical application of a single dose (0.3%) of SA9000 could significantly reduce intraocular pressure (IOP) (approximately 25% vs. fellow untreated eye) but caused significant conjunctival hyperemia. Since this hyperemia was likely the result of its inherent thiol reactivity, SA9000 was formulated with equimolar cysteine, an exogenous thiol donor. The administration of increasing SA9000-cysteine adduct concentrations (0.3%, 0.6%, 0.9%) demonstrated that they cause less ocular irritation than unadducted SA9000 but could still significantly reduce IOP (0.3%: 8.7 +/- 2%; 0.6%: 14.4 +/- 5%; 0.9%: 23.3 +/- 4.4%) versus untreated contralateral control eyes. CONCLUSIONS: These data suggest that novel thiol donor adduction can improve the ocular bioavailability and tolerability of SA9000. SA9000-cysteine prodrugs may represent a new option for the topical treatment of glaucoma.

The release and transdermal penetration of baclofen formulated in a poloxamer lecithin organogel.

The purpose of this study was to evaluate the in vitro release and ex vivo penetration of baclofen following incorporation into a 2% poloxamer lecithin organogel. Franz cells were utilized for both the release and penetration studies. Semi-permeable dialysis membranes were used as the model skin for the penetration study. Baclofen release and penetration at predetermined time points were assessed using high-performamce liquid chromatographic analysis. Results demonstrated that baclofen release from the poloxamer lecithin organogel was significantly higher than its penetration through porcine skin. The amount of baclofen released by the poloxamer lecithin organogel was linear up to 12 hours. Approximately 20% of applied drug was released over the duration of the study period. In comparison with drug released, the ex vivo penetration of baclofen through porcine skin was very low with only minute detectable quantities (significantly less than 1%) after the 12-hour study period. These results suggest that the request to include baclofen into a compounded poloxamer lecithin organogel should be approached cautiously by compounding pharmacists.

Tetradecylmaltoside (TDM) enhances in vitro and in vivo intestinal absorption of enoxaparin, a low molecular weight heparin.

Tetradecylmaltoside (TDM) was evaluated as a potential gastrointestinal absorption enhancer for low molecular weight heparin (LMWH), enoxaparin. The in vitro efficacy of TDM (0.0625, 0.125 and 0.25% w/v) in enhancing transport of 3H-enoxaparin or 14C-mannitol was investigated in human colonic epithelial cells (C2BBel). Metabolic stability of the drug was determined in C2BBel cell extracts. Transepithelial electrical resistance (TEER) was measured before and after exposure of the cells to TDM. Enoxaparin was further administered to anesthetized Sprague-Dawley rats in oral formulations in the absence or presence of increasing concentrations of TDM and drug absorption was monitored by measuring anti-factor Xa activity in rat blood. In vitro permeability study shows that apparent permeability (Papp) of 3H-enoxaparin across C2BBe1 cells was increased by 8-fold in the presence of 0.0625% TDM compared to untreated cells. The movement of 14C-mannitol across the cell monolayer followed a similar pattern in the presence of increasing concentrations of TDM. No degradation or depolymerization of enoxaparin was observed when the drug was incubated in C2BBel cell extract. TEER was reversible after 60 min exposure of the cells to 0.0625% (w/v) TDM. Oral formulations of enoxaparin containing TDM administered to anesthetized rats significantly and rapidly increased gastrointestinal absorption as compared to those animals which received enoxaparin plus saline (p < 0.05). In the presence of 0.125% TDM in the formulation, enoxaparin oral bioavailability was increased by 2.5-fold compared to the saline control group. Overall, the data on the effect of TDM on the in vitro and in vivo intestinal permeation of enoxaparin suggest that TDM may represent a promising excipient for use in oral LMWH formulations.

Correlation of tetradecylmaltoside induced increases in nasal peptide drug delivery with morphological changes in nasal epithelial cells.

The effect of tetradecylmaltoside (TDM) on nasal peptide drug absorption was assessed with four peptides of distinct molecular size: insulin (5.7 kDa), leptin (16 kDa), somatropin (22.1 kDa), and epoetin alfa (30.4 kDa). The nasal uptake of the smallest peptides, insulin and leptin, was significantly increased at a TDM concentration of only 0.06%. The uptake of somatropin was significantly increased when concentrations of 0.125% or more were used. The uptake of the largest peptide, epoetin alfa, was not significantly increased, in the presence of 0.125-0.5% TDM. Light microscopy revealed that formulations containing 0.125% TDM caused moderate alterations in nasal epithelial cell morphology, while higher concentrations of TDM (0.5%), caused more extensive morphological changes. Following treatment with 0.125% TDM, the distribution of cilia was altered and the number of pinocytotic vesicles was increased, at a time that correlated with increased nasal absorption of insulin. Consistent with these findings, FITC-insulin applied nasally in the absence of TDM did not enter nasal epithelial cells, whereas FITC-insulin co-administered with 0.125% TDM was internalized into the cells, with a uniform distribution, consistent with transcellular movement of the peptide through the cells.

Absorption enhancers in pulmonary protein delivery.

Extensive research efforts have been directed towards the systemic administration of therapeutic proteins and poorly absorbed macromolecules via various nontraditional, injection-free administration sites such as the lung. As a portal for noninvasive delivery, pulmonary administration possesses several attractive features including a large surface area for drug absorption. Nevertheless, achieving substantial bioavailability of proteins and macromolecules by this route has remained a challenge, chiefly due to poor absorption across the epithelium. The lungs are relatively impermeable to most drugs when formulated without an absorption enhancer/promoter. In an attempt to circumvent this problem, many novel absorption promoters have been tested for enhancing the systemic availability of drugs from the lungs. Various protease inhibitors, surfactants, lipids, polymers and agents from other classes have been tested for their efficacy in improving the systemic availability of protein and macromolecular drugs after pulmonary administration. The purpose of this article is to provide the reader with a summary of recent advances made in the field of pulmonary protein delivery utilizing absorption enhancers. This report reviews the various agents used to increase the bioavailability of these drugs from the lungs, their mechanisms of action and effectiveness, and their potential for toxicity.

Effects of the permeability enhancers, tetradecylmaltoside and dimethyl-beta-cyclodextrin, on insulin movement across human bronchial epithelial cells (16HBE14o-).

The permeability of human bronchial epithelial cells (16HBE14o(-)) to radiolabelled insulin ([125I]insulin) formulated in the absence or presence of two different saccharide-containing permeability enhancers was investigated. In the absence of either enhancer, mannitol permeability and transepithelial electrical resistance (R(TE)) remained essentially unaffected for the duration of a 2-h experiment. Addition of either 0.125% tetradecylmaltoside (TDM) or 1% dimethyl-beta-cyclodextrin (DMBCD) to the apical surface of cells resulted in increased mannitol permeability and decreased R(TE), suggesting a loosening of cellular tight junctions and a concomitant increase in paracellular movement. Addition of [125I]insulin to the apical side of 16HBE14o(-) cells in the absence or presence of 1% DMBCD resulted in little or no [125I]insulin movement to the basolateral chamber or degradation in the apical chamber. However, in the presence of 0.125% TDM, the amount of intact [125I]insulin remaining in the apical chamber was substantially decreased, while [125I]insulin and 125I-labeled fragments were recovered on the basolateral side of the cells after 2 h. These findings provide evidence that the loosening of the tight junctions between cells achieved with DMBCD is not sufficient to stimulate transepithelial insulin movement, whereas exposure to 0.125% TDM causes an increase in [125I]insulin permeation and degradation.

Sucrose cocoate, a component of cosmetic preparations, enhances nasal and ocular peptide absorption.

Sucrose cocoate (SL-40), an emulsifier employed in emollient, skin-moisturizing cosmetic formulations, contains a mixture of sucrose esters of coconut fatty acids in aqueous ethanol solution. In order to determine its potential utility in enhancing nasal and ocular drug delivery, absorption studies were performed in anesthetized Sprague-Dawley male rats with calcitonin and insulin, two distinct therapeutic peptides. Administration of a nasal insulin formulation containing 0.5% sucrose cocoate caused a rapid and significant increase in plasma insulin levels, with a concomitant decrease in blood glucose levels. When insulin was administered ocularly in the presence of 0.5% sucrose cocoate, a smaller increase in plasma insulin levels, and a decrease in blood glucose levels, were observed. Administration of a nasal calcitonin formulation containing 0.5% sucrose cocoate caused a rapid increase in plasma calcitonin levels and a concomitant decrease in plasma calcium levels. Mass spectrometric analyses were used to characterize the nature of the sucrose fatty acid esters in the mixture. The most abundant sucrose ester in sucrose cocoate was sucrose monododecanoate, with smaller amounts of sucrose monodecanoate and sucrose monotetradecanoate. In vivo experiments confirmed that this ester was an effective enhancer of nasal peptide drug absorption.

Synthetic long-chain alkyl maltosides and alkyl sucrose esters as enhancers of nasal insulin absorption.

A series of new glycosides with extended alkyl side-chains (C(13-16)) linked to maltose or sucrose were synthesized and tested for their efficacy in enhancing nasal insulin absorption in anesthetized rats. The new reagents were compared to previously tested alkylglycosides with shorter alkyl side chains (C(8-12)). Dose-response studies revealed that within the family of alkylmaltoside derivatives, (C(8-16)), maximal increases in insulin absorption took place when tetradecylmaltoside (C(14)) was added to the formulation. Pentadecylmaltoside (C(15)) and hexadecylmaltoside (C(16)) were less potent at increasing insulin absorption, although both reagents achieved maximal effects when used at higher concentrations. Within the family of alkanoylsucrose derivatives, tridecanoylsucrose (C(13)) and tetradecanoylsucrose (C(14)) were most potent at increasing insulin absorption. Cross-comparisons between alkylmaltoses and alkanoylsucroses showed that the alkyl chain length had a greater impact than the glycoside moiety in determining the potency of a potential insulin-absorption enhancing agent. When tetradecylmaltoside was applied to the nasal mucosa 15 min before insulin was applied, the enhanced insulin absorption was still observed.